The coupler panel is an important part of the rail vehicle. In order to study its deformation and residual stress after welding,based on thermal elastoplastic method,taking 6005 A-T6 aluminum alloy coupler panel as the research object,the multi-layer welding deformation and residual stress field were numerically simulated,and the process optimization plan was put forward. The results show that there is a large longitudinal residual tensile stress in the vicinity of the weld seam after the welding of the coupler,and the transverse residual stress in the arcing place and the arc extinguish place is higher. The maximum equivalent stress of Von-Mises occurs at the joint of the front weld and the back weld. By setting proper reverse deformation,the welding deformation can be effectively reduced without affecting the residual stress,while ensuring the flatness and bearing capacity of the coupler panel. The research results have certain guiding significance for the actual welding production of the coupler panel.